Boring bar assembly



March 12,1957 B VJ BRETZ BORING BAR ASSEMBLY Filed June 27, 1956 INVENTOR.

BERNARD J. BRETZ United States Patent 0 BORING BAR ASSEMBLY Bernard J. Bretz, Royal Oak, Mich.

Application June 27, 1956, Serial No. 594,233

10 Claims. (Cl. 77--56) This invention relates to improvements in boring bar assemblies. The invention aims, among other things, to provide a boring bar assembly including means for: holding a small and relatively inexpensive tool bit immovable relative to the bar; simply and accurately adjusting the radial projection of the tool bit; and utilizing the bar itself for directly supporting the inner face of the tool bit at all adjusted positions of the latter to pre vent the possibility of rearward slippage of the bit when a cut is being taken.

Another object of the invention is to provide a boring bar assembly wherein an eccentric annular groove is formed in the bar against the base of which the inner face of the tool bit rests at all adjusted positions to prevent rearward slippage of the bit.

A further object of the invention is to provide such a boring bar assembly wherein the opposite sides of the groove are inwardly inclined toward one another to support correspondingly inclined sides of arcuate members mounted for rotary adjustment in the groove; and wherein one of the arcuate members has a radial opening therethrough for the passage of the tool bit and is radially split intermediately of its width and through the opening so that when inward pressure is exerted on that arcuate member the tool bit is held immovable.

A further object of the invention is to provide such a boring bar assembly including means for outwardly forcing one side of an annular member which encircles the arcuate members so that the opposite side of the annular member exerts inward pressure against the tool bit supporting arcuate member and thereby causes the latter to hold the tool bit immovable.

Yet another object of the invention is to provide such a boring bar assembly in a slightly modified form of which a plurality of circumferentially spaced tool bits are mounted in openings formed through one of the arcuate members, and the eccentricity of the base of the groove increases the radial projection of all the tool bits uniformly as their arcuate supporting member is turned in one direction therein.

Having thus stated some of the objects and advantages of the invention I will now describe it more fully with the aid of the accompanying drawing, in which:

Figure 1 is a plan view showing the invention,

Figure 2 is a side elevation thereof, and

Figure 3 is a section on the line 33 of Figure 1.

Figure 4 is a detail showing a slight modification.

Figure 5 is a section on the line 5-5 of Figure 7.

Figure 6 is a detail showing a portion of one arcuate member and the annular member in Figure 5, and

Figure 7 is a front elevation of another modified form of the invention on a somewhat reduced scale.

Referring to the drawing, 1 designates a boring bar having an annular groove 2 formed therein intermediately of its length. The base 3 of the groove is eccentric and from the circumference of the bar the opposite sides 4 of the groove are inwardly inclined toward one another 'ice for a portion of their depth and their inner extremities 4a are preferably parallel so that the width of the base is the same throughout its circumference.

Mounted in the groove 2 for rotary adjustment therein are a plurality of somewhat resilient arcuate members 5 and 5a having their opposite sides 6 and 6a, respectively, tapered to bear against the inclined sides 4 of the groove throughout their depth. The outer radius of the arcuate members 5 and 5a is slightly greater than that of the bar 1. The arcuate member 5 also has a slot '7 formed circumferentially therethrough intermediately of its length and width, and the slot usually extends around the member for the major portion of its length.

A radial opening 8 is also formed through the arcuate member 5 substantially centrally of its circumferential length. This opening preferably extends on both sides of the slot 7. Mounted in the opening it is a tool bit 9 which is held immovable when the arcuate member is forced inward in the groove 2 by means hereinafter de scribed. The inner face of the tool bit rests against the base 3 of the groove, and a cutting edge 10 is formed on its outer face.

Mounted around the arcuate members 5 and 5a, and preferably wider than the latter, is a somewhat resilient annular member 11 of slightly greater bore than the diameter of the bar 1, and formed through the annular member is an aperture 12 through which the tool bit 9 projects and is freely movable. Thus the tool bit is adapted to be moved radially outward by the base 2 of the groove upon rotary adjustment in. one direction of the arcuate member 5 and the annular member 11.

in order to hold the arcuate member 5 and the tool bit 9 immovable relative to the bar 1 at any rotary position of the arcuate member around the latter means are provided for forcing the arcuate member 5a and the adjacent portion of the annular member 11 apart and thereby causing the opposite side of the member 11 to exert inward pressure against the outer face of the arcuate member 5.

In the arrangement shown in Figures 1 to 3, inclusive, a tapped radial opening 14 is formed through the arcuate member 5a to receive a screw 15 having a countershank head 16 to receive a wrench indicated at 17, which is inserted through an aperture 18 formed radially through the annular member 11. It will be noted that the aper ture 18 is materially smaller than the screw 15 so that the latter, when outwardly tightened against the bore of the annular member, has ample bearing against the latter around the aperture 18.

In the modification shown in Figure 4 a tapped radial opening 19 is formed through the annular member 11 to receive a screw 2% which is tightened against the outer face of the arcuate member 52 thereby exerting outward pressure against the portion of the annular member adjacent the screw and forcing the opposite side of the said member 11 and the arcuate member :3 inwardly.

It is of course understood that in both Figures 3 and 4 the distortion of the annular member 11 caused by outward pressure exerted through the screw 15, or 20, is greatly exaggerated.

In the modification shown in Figures 5 to 7, inclusive, the arcuate member 5 is provided with a plurality of circumferentially spaced radial openings 8, instead of a single opening, and corresponding apertures 12 are provided through the annular member 11. Mounted in each opening 8 is a tool bit 9 which again bears against the base 3 of the groove. In this case a plurality of means may be employed for forcing the adjacent faces of the arcuate member 5a and the annular member 11 apart. The means employed in the present instance consists of a screw 15 in threaded engagement with the arcuate member 5a and accessible through a radial opening 18 formed 3 through the annular member 11, and also a screw 20 tapped through an opening 19 formed through the annular member 11 and bearing against the outer face of the arcuate member a. Moreover the screws 15 and are circumferentially spaced from one another. When this arrangement is employed, upon rotation of the arcuate members 5 and 5a and the annular member 11 relative to the bar to increase the outward projection of the tool bits, all the latter are outwardly advanced an equal distance by the eccentricity of the base 3 so that their relative setting remains the same.

To facilitate accurate adjustment of the tool bit, or bits, when increasing their outward projection, coacting graduations 21 and 22 may be provided on the bar 1 and annular member ill, respectively. In the present instance a single graduation 22 is provided on the annular member and the graduations 21 are circularly spaced so that as the graduation 22 registers with each succeeding graduation 21 the outward projection of the tool bit, or bits, is increased, say one-thousandth of an inch. Further to facilitate rotation of the annular member 11, and with it the arcuate members 5 and 5a, the said member 11 is preferably knurled at 23 intermediately of its width around its outer circumference. The screws are substantially diametrically opposite the tool bits.

While in the foregoing the preferred embodiments of the invention have been described and shown, it is understood that altcrations and modifications may be made thereto provided the said alterations and modifications fall wtihin the scope of the appended claims.

What I claim is:

1. A boring bar assembly comprising a bar having an annular groove formed therein intermediately of its length, an arcuate member mounted for rotary adjustment in the groove and having a substantially radial opening therethrough, said member being slotted from said opening to render it laterally compressible, a tool bit mounted in the opening and projecting outwardly therefrom, the inner face of the bit bearing against the base of the groove, coacting means on the bar and the arcuate member for compressing the member and holding the tool bit immovable when said member is forced inwardly in the groove, and means mounted around the bar for exerting inward pressure on the arcuate member.

2. A boring bar assembly comprising a bar having an annular groove formed therein intermediately of its length, an arcuate member mounted for rotary adjustment in the groove and having a substantially radial opening therethrough, said member being slotted from said open ing to render it laterally compressible, a tool bit mounted in the opening and projecting outwardly therefrom, the inner face of the bit bearing against the base of the groove, coacting means on the bar and the arcuate member for compressing the member and holding the tool bit immovable when said member is forced inwardly in the groove, a second arcuate member in the groove, an annular member encircling the bar and both arcuate members, and means for forcing the second arcuate member and the annular member apart and interposed between these members whereby the annular member exerts inward pressure against the first named arcuate member.

3. A boring bar assembly comprising a bar having an eccentric annular groove formed therein, an arcuate member mounted for rotary adjustment in the groove and having a substantially radial opening therethrough, said member being slotted through the opening to render it laterally compressible, a tool bit mounted in the opening and projecting therefrom, the base of the eccentric groove being adapted to support the inner face of the tool bit whereby upon rotary adjustment of the member in one direction the outward projection of the tool bit is increased, coacting means on the bar and the arcuate member for compressing the member and holding the tool bit immovable when said member is forced inwardly in the groove, and means mounted around the bar for exerting inward pressure against the arcuate member.

4. A boring bar assembly comprising a bar having an eccentric annular groove formed therein, an arcuate member mounted for rotary adjustment in the groove and having a substantially radial opening therethrough, said member being slotted from the opening to render it laterally compressible, a tool bit mounted in the opening and projecting therefrom, the base of the eccentric groove being adapted to support the inner face of the tool bit whereby upon rotary adjustment of the member in one direction the outward projection of the tool bit is increased, coacting means on the bar and the arcuate member for compressing said member and holding the tool bit immovable when the member is forced inwardly in the groove, a second arcuate member mounted in the groove, an annular member encircling the bar and both arcuate members and apertured for the passage of the tool bit therethrough, and means for forcing the second arcuate member and the annular member apart and intcrposed between these members whereby the annular member exerts inward pressure against the first named arcuate member.

5. A boring bar assembly assembly comprising a bar having an eccentric annular groove therein the opposite sides of which are inwardly inclined toward one another, an arcuate member having its opposite sides inwardly inclined to coact with the inclined sides of the groove, said member being mounted for rotary adjustment in the groove, said member having a substantially radial opening therethrough and being slotted from said opening to render the member laterally compressible, a tool bit mounted in the opening and projecting outwardly therefrom, the inner face of the tool bit being adapted to rest against the base of the groove whereby upon rotary adjustment of the member in one direction the outward projection of the tool bit is increased, a second arcuate member mounted in the groove, an annular member encircling the bar and both arcuate members and apertured for the passage of the tool bit therethrough, and means for forcing the second arcuate member and the annular member apart including a screw in threaded engagement with one of the members for exerting pressure against the other member whereby the annular member exerts inward pressure against the first named arcuate member and compresses it laterally to grip the tool bit.

6. The combination in claim 5, wherein the screw is in threaded engagement with the annular member and is adapted to exert pressure against the outer face of the second arcuate member.

7. The combination in claim 5, wherein the screw is in threaded engagement with the second arcuate member and is adapted to exert pressure against the bore of the an nular member.

8. The combination in claim 5, wherein the screw is substantially diagrammatically opposite the tool bit.

9. A boring bar assembly comprising a bar having an eccentric annular groove therein, an arcuate member mounted for rotary adjustment around the groove and having circuinferentially spaced openings formed therethrough, tool bits projecting outwardly through the openings, the inner faces of the bits bearing against the base of the groove whereby upon rotation of the member in one direction the outward projection of all the bits is uniformly increased, said member being slotted from said openings to render it laterally compressible, coacting means on the bar and the arcuate member for compressing the member and holding the tool bits immovable when said member is forced inwardly in the groove, and means mounted around the bar for exerting inward pres sure on the arcuate member.

10. The combination in claim. 9, wherein the means mounted around the bar consists of a second arcuate member mounted in the groove, an annular member 2,784,617 5 encircling the bar and both the arcuate members and References Cited in the file of this patent apertured for the passage of the tool bits therethrough, UNITED STATES PATENTS and means for forcing the second arcuate member and the annular member apart and interposed between said 2381806 Clark 1945 members whereby pressure is exerted inwardly on the first 5 FOREIGN PATENTS named arcuate member by said annular member. 724,432 Germany 26, 1942 

